The present invention relates, generally, to apparatus and methods for reducing rotational friction, shocks and vibrations associated with bearing a rotatable shaft (2) within a subterranean bore, usable with various inventions of the present inventor that are generally described in United Kingdom Patent Number 2465478, entitled “Apparatus And Methods For Operating A Plurality Of Wells Through A Single Bore”; United Kingdom Patent Number GB2471760B, first published under GB2471760A on 12 Jan. 2011, and PCT Patent Application GB2010/051108, both entitled “Apparatus And Methods For A Sealing Subterranean Borehole And Performing Other Cable Downhole Rotary Operations,” and both filed Jul. 5, 2010; and United Kingdom Patent Number GB2475626B, entitled “Managed Pressure Conduit Assembly Systems And Methods For Using a Passageway Through Subterranean Strata,” filed Dec. 23, 2010 and first published under GB2475626A on 25 May 2011, all of which are incorporated herein in their entirety by reference.
The embodiments of the present invention can be usable with rotary drilling tools for debris and drilling fluid homogenization, anti-stall, anti-vibration and directional drilling control relating to controlling weight-on-bit and/or directional orientation during drilling operations, wherein the debris homogenised into the drilling fluid is also usable as lost circulation material (LCM).
Additionally, the present invention relates, generally, to a steerable rotary drilling device and methods for directional drilling with jointed, coiled tubing and/or cable conveyed rotary drilling strings, of the present invention and inventor, wherein the debris and drilling fluid homogenization is usable to prevent or inhibit the initiation of strata fractures while the fluid dampening effective of, for example a rotor stator fluid bearing is usable to prevent or inhibit stalling and/or adverse shock or vibration of rotary drilling strings during drilling and/or directional drilling operations, for any combination of hole angle, curvature rate, and bit load.
Cable drilling assemblies of the present invention and inventor may be used as or with a downhole fluid positive displacement motor (PDM), while jointed drill pipe, and/or coiled tubing drilling assemblies may be used with a PDM and the present invention to rotate a boring drill bit.
A downhole tool that homogenizes drilling rock debris into the fluid circulation system, reacts to frictional factors and reduces the occurrence of adverse shocks, stick slip and/or vibration will increase overall drilling efficiency by: i) increasing the effective time of the downhole assembly's associated boring bit engagement with strata while drilling, thus increasing the average rate of penetration; ii) decreasing the damaging shock and vibrational forces to the downhole assembly, thereby decreasing occurrence of downhole failure; iii) increasing the pressure capacity of the circulating system with increased fluid carrying capacity through homogenization and disposal of boring bit cuttings through lost circulation material (LCM) compaction in the sidewall or screening at surface, thus increasing the penetration rate limitations imposed by drilling fluid loses and debris loading prior to removal; and iv) decreasing the time spent tripping for all strings; and v) fatigue cycles associated with cable and coiled tubing strings; thus increasing the rate of penetration and distance drilled before tripping for repairs and/or replacement.
More efficient drilling operations reduce overall required resource costs through a conventional time and cost relationship, and reducing the forces exerted on downhole tools also increases their useful life.
During drilling operations, regardless of whether rotary equipment, e.g. a top drive, is located at surface or a PDM is used downhole, it is desirable to support a rotating shaft or conduit about the axis of boring so as to effectively place weigh on bit (WOB). For complex closed loop rotary steerable systems, e.g., one or more gimbaling spherical bearings may be placed on drilling shafts to ensure the proper rotation or movement and/or orientation of the boring bit, relative to the axis. For straight hole or directionally controlled bottom hole drilling assemblies, various centralizing fulcrums or pivot points, generally comprising drilling tools contactable with the borehole sidewall, are used to align the drill string and bit with the desired axis of boring.
Generally, conventional bearings are used for the support of complex closed loops rotary steerable systems (RSS) which often suffer from significant adverse stick slip and vibration limitations that, generally, may not be significant for PDM downhole assemblies. Artisans may sometimes combine a PDM with a RSS to increase the penetration rate in hard drilling areas, but such combinations are not generally easy.
Conventional fluid bearing misalignment between rotating and associated complementary surfaces may affect fluid passage and prevent the fluid bearings from accurately supporting loads, since any such misalignment will adversely affect the gap between, e.g., the rotor and stator surfaces. Generally, fluid bearings depend upon the small gap between rotating and complementary surfaces for lubrication, wherein any misalignment is detrimental to the performance of the bearing to the point of making the bearing inoperable through the lack of lubrication. Additionally non-uniform loading on the shaft or conduit can cause a lack of circular symmetry of loading on the conduit or shaft, resulting in deflection of the ends of the shaft in the bearings which affects the fluid lubricating gap.
Conventional PDM technology uses fluid to positively displace helical lobes of a rotor within the associated helical profiles of a stator, wherein a planned deflection of the rotor within the stator occurs as the rotor rotates about the rotor's and stator's axis. Generally, within a PDM, the rotor is left free to deflect at its upper end with controlled rotation of downhole apparatuses at its lower end.
The present invention may use the defined deflection of a helical lobed rotor within the helical cavities of a stator, or vice versa, to form a fluid bearing to, for example, reduce shocks and vibration in a rotational drilling shaft or homogenize boring bit cuttings within drilling fluid slurry to facilitate removal or use as LCM.
The present invention may also use a spherical bearing or gimballing system, forming part of a helical lobe rotor and stator fluid bearing, to provide a self-aligning fluid bearing pump, which can be usable to drive downhole tools. Alternatively, a helical lobe rotor and stator may be used to automatically compensate for misalignment between the axis of a spaced bearing arrangement and a drilling tool rotational axis so as to compensate for non-uniform circular shocks and vibrations or loads placed on the drilling conduit or shaft, wherein sinusoidal, harmonic or non-uniform vibrations and deflections of the rotating drilling conduit or shaft are fluidly dampened, and wherein such fluid bearings may be applied to a various downhole apparatuses.
Hydrostatic and hydrodynamic conventional thrust and journal bearings, of the fluid or frictionless type, use a predetermined gap between moving parts with a pressurized fluid maintained within said gap or spacing between moving parts to provide rotational lubrication. Hydrostatic bearings continually supply pressurized fluid to and from the spaces between moveable or relatively movable parts. Hydrodynamic bearings supply pressurized fluid between the moving parts by the relative movement of said parts. Hydrostatic bearings are usable where there is significantly, little or no movement between any movable or relatively movable parts, whereas a high rate of relative movement between the parts is necessary for hydrodynamic bearings to pressurize and move fluid so as to maintain the gap between the parts during rotation. Various prior art exists, e.g., Sakamoto, in U.S. Pat. No. 6,837,621 B1, filed 29 Jan. 2003, teaches a hydrodynamic bearing for a submersible pump motor which is neither designed for, nor sufficiently robust for, use within a drill string. Hummes et al., in US 2009/0242276 A1, filed 25 Mar. 2009, teaches a hydrostatic fluid bearing arrangement, which pumps fluid to a bearing or conventional fluid bearing primarily for cooling, wherein the bearing and the pumping flow device are two different mechanisms and are susceptible to vibration from eccentric rotational hydrodynamic profiles. In contrast, the present invention provides a hydrodynamic bearing that combines the pump with the bearing and compensates for eccentrically rotating hydrodynamic profiles using, e.g., helical wrapping bearings.
Conventional drill string stabilizers form crude fluid bearings within the bore hole, which are not generally recognized as such by those practicing in the art of drilling, with the exception of drill pipe protectors used within the casing. Moore, et al., in WO 00/40833, filed 6 Jan. 2000 and Tverlid, in WO 2010/022755 A1, filed 29 Aug. 2008, teach the use of a drill pipe protector as a form of fluid bearing, wherein said protectors are substantially stationary sleeves with flow channels and ports that are clamped onto the smooth outer diameter of a drill pipe or comprise a sealed unit intended primarily to protect the drill pipe and casing from wear. The outside diameter of such protectors are, generally, slightly larger than the drill pipe tool joints and significantly smaller than the casing inside diameter, thus preventing any rotating impellors or hydrodynamic profiles fixed, thereto, from functioning as a hydrodynamic bearing, since such prior art relies primarily upon trapping fluid pumped through the annulus or from within the drill string with optional, rudimentary, centrifugal urging of fluid outward from the smooth rotating surface of the drill pipe.
Components of the bottom hole assembly (BHA) above the boring bit comprising, for example, drilling stabilizers, drill collars and other ancillary equipment, including the associated deployment string, are generally cylindrical and of a smaller diameter than the borehole, so as to permit drilling fluid, generally referred to as drilling mud, and boring bit cuttings debris to flow back to the surface through the annular space between the pipe string and bore hole, wherein the drilling mud reduces the drag of the crude fluid bearings formed between the stabilizers and the wall of the strata bore as the drilling assembly is rotated and urged axially.
As a result, two major elements, comprising tensioned and compressed string portions axially above and below a neutral point, respectively, may incur torsional resonance when a the drill string undergoes harmonic oscillations or shock forces during stick and slip of the drill string, while rotating between the conventional crude fluid bearing stabilizers, which may be inadequately spaced and/or under gauged relative to the bore hole's diameter, and wherein axial inclination or deviational deflection may occur. Improperly configured drill strings may incur significant inefficiencies, comprising torsional loading and harmonic oscillations of sufficient magnitude to cause drill string failure in many cases, especially within rotary coiled tubing and cable string drilling assemblies where rotation of the deployment string may be catastrophic.
Torsional resonance or stick slip for components with high torsional stiffness and modulus of elasticity characteristics, e.g. drill-collars, may also damage drill string components, e.g. boring bit polycrystalline diamond compact (PDC) cutters, through the momentum of torsional loads and/or reverse rotation of the drilling assembly comprising backlash from whirl and stick slip behaviour.
Stick-slip behaviour of a drill string may represent chaotic disturbances in normal operations and destructive torsional resonances of the rotating portion of the drill string heavy drilling loads that depend upon various factors including axial drag, axial shock loading or bit bounce, bit whirl caused by disengagement from the boring face, back-lash or backwards spin resulting from stick-slip that may result in torque shocks and vibration from bit whirl and stick-slip, buckling of rotational components and/or lateral harmonic vibration associated within unsupported portions of the drill string lacking a bore hole bearing, e.g. a stabilizer.
If a drill string is not arranged to naturally balance such destructive axial, torsional and centrifugal forces, adverse rotational forces may become self-sustaining due to the momentum of a continuously rotated mass, e.g. heavy drill collars, and associated harmonic vibrations between or about borehole bearings, whereby stopping rotation or axially withdrawing contact with the boring face may be the only means of countering said destructive forces, once they start.
Successfully avoiding adverse rotary stick-slip and/or managing drill string rotational harmonics to improve the drilling process requires balancing of the rotational driving mechanism, the rotating components, the torsional rigidity of the components and the interaction of the boring bit with the strata being drilled. While each of these factors have an effect, each factor may also affect another factor, thus causing significant complexities, like the interaction between differing rotational sinusoidal harmonics along a drill string, wherein the avoidance of adverse torsional loading and harmonic vibration is difficult because the factors are constantly changing.
With regard to related prior art, McLoughlin and Swietlik, U.S. patent application Ser. No. 12/733,480, propose confining the radial motion of a stabilizer within the borehole using a flexible joint within a drill string stabilizer, thus providing flexibility, within limitations, to the internal attitudinal motion and constraining lateral and torsional movements through the use of an improved stabilizer design that inherently falls short of forming a fluid bearing. The full extent of potentially destructive forces cannot be fully dissipated between the drill string and the sidewall because the design does not actively supply fluid lubrication between the side wall and the drill string stabilizer blade. Additionally, integration with a rotary steerable tool, rotary cable tool compatibility and fluid homogenisation with the associated benefits of debris removal and LCM generation, provided by the present invention, are not present in the teachings of McLoughlin and Swietlik.
As the frequency of harmonic vibrations associated with the rotating drill strings may vary widely across drill string configurations and geologic conditions, timely corrective action from an active hydraulic system responsive to the required active damping of the continuously changing harmonic motion is necessary. Periods of high bit generated vibration frequency and amplitude require active and responsive fluid damping of the BHA to prevent adverse harmonic and torsional rotation and, consequently, feedback to the bit which may further degrade drill string rotation. Adverse harmonic and torsional rotation can be especially problematic for rotary cable tool boring operations.
Unfortunately, despite having significant merit, the technology taught by, e.g., McLoughlin and Swietlik, the present inventor and the present invention can be difficult to deploy due to the risk tolerance of Operators and the oligopolistic nature of large service providers who, understandably, prefer using technology with the highest immediate return, thus making new technology development difficult.
Ultimately solutions to drilling and production operational problems come from field testing and development of new technology; however, well operators face a series of challenges at each stage of a well's lifecycle as they seek to balance the need to maximise economic recovery with the associated reduced net present value of produced assets and subsequent abandonment liabilities, while meeting their obligations for safe and environmentally sensitive operations. After drilling and well construction, when wells lose structural integrity, which may be defined as an apparent present or probable future loss of pressure or fluid bearing capacity and/or general operability, all or portions of a well may be shut-in for maintenance or suspension, or may require immediate plugging and abandonment, potentially leaving producible reserves within the strata that cannot justify the cost of intervention or a new well.
New technology provided by the present invention and others could be proven within unproductive wells if the problems of structure integrity could be addressed. Some of the more frequently reported structural well integrity problems comprise a lack of centralization leading to conduit erosion from thermal cycled movement, corrosion within the well conduit system from, e.g., biological organisms or H2S which forms leaks through or destroys conduits or equipment and/or causes valve failures associated with subsurface safety valves, gas lift valves, annuli valves and other such equipment. Other common well integrity issues include unexplained annulus pressure, connector failures, scale, wear of casings from drilling operations, wellhead growth or shrinkage and xmas or valve tree malfunctions or leaks at the surface or subsea. Such well integrity issues comprise areas where operators are able to, or choose to, test integrity and there are others (such as the internals of a conductor) which they cannot, or do not, test integrity and which may represent a serious risk to economic viability and the environment. Problems within various portions of a well, in particular the annuli, cannot be conventionally accessed without significant intervention or breaking of well barriers, e.g., with a drilling rig, and thus, are a significant cost and safety risk to operators that are unsuitable for conventional rig-less operations.
A primary advantage of using drilling specification rigs for well intervention is the removal of conduits and access to annuli during well intervention and abandonment, wherein the ability to access and determine the condition of the annuli casing and primary cement behind the production conduit or tubing is used to make key decisions regarding the future production and/or abandonment. If well casings are corroded or lack an outer cement sheath, remedial action, e.g. casing milling, may be taken by a drilling rig to provide a permanent barrier. Conversely, the problem may be exacerbated by conventional rig-less well abandonment when blind decisions are made without cement logging access to annuli and attempts to place cement fail, thereby placing another barrier over potentially serious and worsening well integrity issues that can represent a significant future challenge, both technically and economically, even for a drilling rig.
Various apparatuses and methods of the present inventor are usable for benchmarking, developing, testing and improving the present invention and other new technology, wherein said apparatuses and methods relate to the gathering of information that conventional rig-less operations cannot, by providing access and/or space for both measurement devices and sealing materials within unproductive wells. Once such information is gathered, still other apparatuses and methods of the present inventor are usable for benchmarking, developing, testing and improving rig-lessly placed barriers, to mill or shred conduits and casings to expose and bridge across hard impermeable strata or cap rock formations, for the placement of permanent barriers to ensure structural integrity that is necessary for proving the present invention and other new technology within unproductive wells.
In general, age is believed to be the primary cause of structural well integrity problems. The combination of erosion, corrosion and general fatigue failures associated with prolonged field life, particularly within wells exceeding their design lives, together with the poor design, installation and integrity assurance standards associated with the aging well stock is generally responsible for increased frequency of problems over time. These problems can be further exacerbated by, e.g., increasing levels of water cut, production stimulation, and gas lift later in field life.
However, the prevalent conventional consensus is that although age is undoubtedly a significant issue, if it is managed correctly it should not be a cause of structural integrity problems that may cause premature cessation of production. Additionally, fully depleting producing zones through further production prior to abandonment provides an environment of subterranean pressure depletion better suited for placing permanent barriers by lowering the propensity of lighter fluids to enter, e.g., cement during placement.
The embodiments of the present invention may be benchmarked, developed, tested and improved within an unproductive well, thus proving the technology, providing annuli that are accessible and pressure bearing conduits and well barrier elements that are selectively placed at required subterranean depths, between annuli, to allow further intervening in, maintaining, and/or abandoning portions of a well to extend the well life through, e.g., use of the present hydrodynamic fluid bearing, within a drill string, to access and to fully deplete a reservoir for further reducing the risk associated with well barrier element placement and the pollution liability from an improperly abandoned well.
The level of maintenance, intervention and workover operations necessary for well maintenance is restricted by the substantial conventional costs involved. The limited production levels of aging assets often cannot justify the conventional practice of using higher cost drilling rigs, and conventional rig-less technology is generally incapable of accessing various passageways or all annuli within the well.
Therefore, well operators generally place an emphasis on removing troublesome assets from their portfolio and seek to prevent future problems using improved designs, rather than attempting to remedy a poorly designed well, which in turn precipitates a greater focus on asset disposal, well design, installation and/or integrity assurance. Passing the problem on to others with the sale of a well does not, however, solve the issue of abandoning existing and aging wells from a liability viewpoint.
When intervention is required, risk adverse major oil and gas companies generally prefer asset disposal and replacement rather than remediation, favouring sale of aging well assets to smaller companies with lower overheads and higher risk tolerances. Smaller companies, requiring a lower profit margin to cover marginal cost, are generally eager to acquire such marginal assets, but may in future be unable to afford well abandonment, thus putting the liability back to the original owner and preventing sale or creating a false economy for the seller. Low cost reliable rig-less placements of well barrier elements to delay or perform abandonment is critical to major and small companies if aging assets are to be bought and sold and/or used for testing new technologies, to avoid such false economies. Thus, the rotary drilling rig and rig-less apparatuses and methods of the present invention are provable and usable within unproductive wells to place and verify well barrier elements for reliable abandonment and/or drilling, and hence are important to all companies operating, selling and/or buying aging wells.
Therefore, the structural integrity of producing and abandoned wells is critical because the liability of well abandonment cannot be passed on if a well ultimately leaks pollutants to surface, water tables or ocean environments, because most governments hold all previous owners of a well liable for its abandonment and environmental impacts associated with subsequent pollution. Hence the sale of a well liability does not necessarily end the risk when the asset is sold or abandoned unless the final abandonment provides permanent structural integrity.
Embodiments of the present invention are both usable and provable through benchmarking, developing, testing and improving of such new technology within unproductive wells, using rig-less well intervention and maintenance to extend the life of a well by using one aspect for placing well barrier elements, to isolate or abandon a portion of a well, and, then, operating another aspect until no further economic production exists or well integrity prevents further extraction or storage operations. Thereafter, the well may be completely and permanently abandoned for an indefinite time.
A need exists for improved stability of drilling and directional drilling assemblies for jointed and rotary coiled string operations.
A need exists for benchmarking, developing, testing and improving various embodiments of the present invention that can be usable for delaying abandonment, with low cost rig-less operations for placement of well barrier elements. This need is directed to an increased return on invested capital, for both substantially hydrocarbon and substantially water wells, through rig-less side-tracking for marginal production enhancement, suspending and/or abandoning portions of a well, to re-establish or prolong well structural integrity for aging production and storage well assets, and for preventing pollution of subterranean horizons, such as water tables, or surface and ocean environments.
A need exists for benchmarking, developing, testing and improving various embodiments of the present invention which are usable for small operating, foot-print, rig-less well barrier element, placement operations usable to control cost and/or perform operations in a limited space, e.g. electric line or slickline operations, on normally unmanned platforms, from boats over subsea wells or in environmentally sensitive area, e.g. permafrost areas, where a hostile environment and environmental impact are concerns. A related need also exists for benchmarking, developing, testing and improving various embodiments of the present invention which are usable for working within a closed pressure controlled envelope to prevent exposing both operating personnel and the environment to the risk of losing control of subterranean pressures if a well intervention kill weight fluid column is lost to, e.g., subterranean fractures.
A need exists for benchmarking, developing, testing and improving various embodiments of the present invention that are usable for avoiding the high cost of drilling rigs, with a rig-less system capable of suspending, side-tracking and/or abandoning onshore and offshore, surface and subsea, substantially hydrocarbon and substantially water wells, using published conventional best practices for placement of industry acceptable permanent abandonment well barrier elements.
A need exists for benchmarking, developing, testing and improving various embodiments of the present invention that are usable for preventing risks and removing the cost of protecting personnel and the environment from well equipment contaminated with, e.g., radioactive materials and scale, by rig-lessly placing abandonment barriers and leaving equipment downhole. A further need exists for benchmarking, developing, testing and improving new technology that is usable to rig-lessly side-track or fracture portions of a well to dispose of hazardous materials resulting from circulation of the well's fluid column during suspension, side-tracking and abandonment operations.
A need exists for benchmarking, developing, testing and improving various embodiments of the present invention that are usable for marginal production enhancement, which can be usable to offset operating costs until final abandonment occurs, including rig-lessly providing well integrity while waiting until an abandonment campaign across a plurality of wells can be used to further reduce costs.
A need exists for benchmarking, developing, testing and improving the technology of the present invention within unproductive wells to reduce the abandonment liability for operators, while meeting their obligations of structural well integrity for safe and environmentally sensitive well operations, suspension and abandonment in an economic manner, which is consistent with providing a hydrodynamic drill string bearing for exploration of new reserves to meet our world's growing demand for hydrocarbons by reducing adverse friction and vibration within drilling rig rotated, boring strings and lower cost, rig-less, side-tracking and boring strings, which can be usable to, e.g., prevent marginal recoverable reserves from being left within the strata due to higher operating overhead requirements that have made such recoverable reserves uneconomic.
Various aspects of the present invention address at least some of these needs.